Size Effect on Concrete Shear Strength in Beams Reinforced with FRP Bars

The understanding of size effect on the concrete shear strength of beams reinforced with fiber-reinforced polymer (FRP) bars is of fundamental and practical significance. The calibration and verification of the ACI 440 shear design algorithm has been mainly based on experimental results from specimens with a maximum effective depth of 360 mm (14.19 in.), which are not always representative of large-scale applications. In this paper, the results of laboratory tests on scaled FRP-reinforced concrete beams without shear reinforcement, having a maximum effective depth of 883 mm (34.75 in.), are presented. Based also on results available in the literature for normal-strength concrete, the scaling of strength is discussed in relation to effective depth, reinforcement ratio, aggregate size, and presence of minimum shear reinforcement and longitudinal skin reinforcement. Representative North American design algorithms that account for the shear force being resisted primarily by the uncracked concrete in compression (ACI) and through aggregate interlock (CSA) are then assessed.